Continuously variable transmissions (CVT) for vehicles for example comprise a primary pulley which inputs the rotation of the engine, a secondary pulley which outputs this rotation to the drive wheels, and a V-belt which transmits the rotation of the primary pulley to the secondary pulley.
In such a CVT, the ratio of the rotational speeds of the primary pulley and secondary pulley, i.e., the speed ratio, is continuously varied by using hydraulic pressure to vary the ratio of the contact radius of the V-belt with the primary pulley and the contact radius of the V-belt with the secondary pulley.
Tokkai Hei 9-329229 issued by the Japan Patent Office in 1997 discloses a slight correction of the target speed ratio of the transmission in the direction of decrease, i.e., in the up-shift direction, immediately after the vehicle has started to move in order to achieve smooth start-up of the vehicle.